1. Field of the Invention
The invention relates to a vehicle bearing device that supports a wheel of an automobile, or the like.
2. Description of Related Art
For example, a bearing device that supports a wheel of an automobile includes a hub spindle 101, an inner ring 102, an outer ring 103 and an annular pulsar ring 105 as shown in FIG. 4 (for example, see Japanese Patent Application Publication No, 2000-211310 (JP 2000-211310 A). The inner ring 102 is fitted to an outer periphery of an end portion of the hub spindle 101. The outer ring 103 is arranged coaxially with the hub spindle 101, on the radially outer side of the hub spindle 101 and the inner ring 102 via rollers arranged in two rows, that is, via first tapered rollers 104a and second tapered rollers 104b. The pulsar ring 105 is fitted to the outer periphery of the hub spindle 101. A sensor (not shown), which detects the rotation of the pulsar ring 105 that rotates together with the hub spindle 101, is fixed to the outer ring 103. The rotation speed of the wheel, used to control an anti-lock brake system, or the like, is obtained based on the detected result of the sensor.
The hub spindle 101 has a flange 111, a large rib surface 112, an inner raceway surface 113, a large-diameter portion 114, an intermediate-diameter portion 115 and a small-diameter portion 116 that are arranged in this order from one axial end portion of the outer periphery toward the other axial end portion of the outer periphery. The wheel (not shown) is fitted to the flange 111. A large-diameter-side end face of each of the first tapered rollers 104a is in sliding-contact with the large rib surface 112. The first tapered rollers 104a roll on the inner raceway surface 113. The outside diameter of the intermediate-diameter portion 115 is smaller than the outside diameter of the large-diameter portion 114. The outside diameter of the small-diameter portion 116 is smaller than the outside diameter of the intermediate-diameter portion 115. The pulsar ring 105 is fitted to the outer periphery of the intermediate-diameter portion 115, and the inner ring 102 is fitted to the outer periphery of the small-diameter portion 116.
An annular first grinding undercut portion 119a, which is a recess in a sectional view, is formed, through turning, at the end portion, on the large rib surface 112-side, of the inner raceway surface 113 of the hub spindle 101 of such a vehicle bearing device. Due to the first grinding undercut portion 119a, the end portion, on the large rib surface 112-side, of the inner raceway surface 113 does not contact the corner, on the large-diameter end side, of each first tapered roller 104a. In addition, an annular second grinding undercut portion 119b, which is a recess in a sectional view, is formed, through turning, at the end portion, on the large-diameter portion 114-side, of the inner raceway surface 113. Due to the annular second grinding undercut portion 119b, a play is provided for each first tapered roller 104a in the axial direction. Furthermore, an annular third grinding undercut portion 119c, which is a recess in sectional view, is formed, through turning, at the end portion, on the large-diameter portion 114-side, of the outer peripheral surface of the intermediate-diameter portion 115. Due to the annular third grinding undercut portion 119c, a grinding stone, or the like, does not interfere with a step surface 118 when grinding is performed on the outer peripheral surface of the intermediate-diameter portion 115.
In the existing vehicle bearing device, the first to third grinding undercut portions 119a to 119c formed on the outer periphery of the hub spindle 101 are formed into different shapes as shown in FIG. 4. Therefore, when the first to third grinding undercut portions 119a to 119c are formed through turning, turning tools, such as a tool and a tip, need to be changed based on the shapes of the grinding undercut portions 119a to 119c or the positioned angle of a turning tool relative to the hub spindle 101 needs to be changed. Therefore, there is a problem that the turning process for the grinding undercut portions 119a to 119c is complex, which reduces the efficiency of manufacturing the hub spindle 101.